The present invention disclosed herein relates to a semiconductor device and a method of forming the same, and more particularly, to a phase change memory device and a method of forming the same.
A state of a phase change material can change into a crystalline state or an amorphous state by varying a temperature of a supplied heat and/or a heat supplying time. That is, after supplying a higher temperature than a melting temperature into the phase change material, the phase change material is rapidly cooled down to change into an amorphous state. Unlike this, after supplying a lower temperature than a melting temperature into the phase change material, the phase change material is slowly cooled down to change into a crystalline state. A heat for changing a state of the phase change material is Joule's heat. Joule's heat is generated using the amount of an operation current that flows through the phase change material and/or the resistivity of electrodes connected to the phase change material. A state of the phase change material changes by adjusting a supplying time and a temperature of Joule's heat.
On the other hand, a phase change memory device with a metal pattern, which contacts the entire top surface of the phase change material, has been suggested. The metal pattern is used as one electrode contacting the phase change material. However, a metal in the metal pattern spreads into the phase change material such that characteristics of the phase change material can be changed. Accordingly, malfunction can occur in the phase change material. To resolve theses limitations, the phase change material can be thickly formed. However, if the phase change material is thick, a program region of the phase change material increases such that an amount of a current used in an erase and/or write operation increases. Accordingly, power consumption of the phase change memory device increases, and the phase change memory device cannot be easily integrated.